1. Field of the Invention
The present invention relates to soldering tips and soldering devices having soldering tips made from copper/iron composites, and methods of making same.
2. Related Art
Copper is a particularly desirable material for forming tips on soldering devices because of its excellent thermal conductivity and good wetting properties. To protect copper soldering tips from oxidation, various methods have been employed. One accepted method is to electroplate the soldering tip with nickel.
A problem with copper soldering tips is that copper is very soluble in tin; thus, some of the copper tip dissolves when contacted with molten solder. This results in deep pitting of the copper tips requiring frequent dressing by filing or grinding. A common technique used to prevent pitting is electroplating iron onto the copper tips.
Another technique which has been suggested to prepare soldering tips is to apply coatings to copper particles and sinter together the coated particles. U.S. Pat. No. 2,679,223 (Franklin) discloses a method for making a soldering tip in which copper particles are agitated and coated with a thin layer of iron, e.g., the copper particles are electroplated in a stirred solution of ferrous chloride. In the next step, the coated particles are compressed and sintered together at 1800.degree. F. to 1900.degree. F. for about three hours, cooled, and then, to form a more suitably dense material, compressed and sintered a second time, and finally compressed a third time. Franklin suggests that the weight of the iron coatings be 10% or less of the weight of the coated particles. It is not believed that this process has ever been used commercially.
U.S. Pat. No. 3,651,306 (Glyptis) suggests the preparation of a porous soldering tip made of copper particles with tin coatings in which the tin functions as a binder during sintering of the particles. The voids in the porous tip are filled by vacuum impregnation with a solder material. During operation capillary action keeps the molten solder material within the tip of the soldering device.
The various soldering tips and methods for making soldering tips described above have a variety of disadvantages. Coatings on soldering tips such as nickel or iron coatings have a significantly lower thermal conductivity than copper and therefore these coatings must be thinly applied. As a result, the coatings may crack or be scratched and the underlying copper is then subject to relatively rapid erosion. Techniques that require coating of copper particles prior to forming a tip have undesirable processing requirements such as electroplating or other coating processes and the need for multiple sintering steps.
Thus there remains a need for durable, high thermally conductive soldering iron tips and methods for making soldering iron tips by simple and inexpensive processes. There is also a need for novel alloy composites that have properties of thermal conductance and resistance to erosion by the tin content of the solder, which makes them suitable for use in soldering tips.